Utilities/interface/ESInputTag.h

0001 #ifndef FWCore_Utilities_ESInputTag_h
0002 #define FWCore_Utilities_ESInputTag_h
0003 // -*- C++ -*-
0004 //
0005 // Package:     Utilities
0006 // Class  :     ESInputTag
0007 //
0008 /**\class ESInputTag ESInputTag.h FWCore/Utilities/interface/ESInputTag.h
0009
0010  Description: Parameter type used to denote how data should be obtained from the EventSetup
0011
0012  Usage:
0013     The ESInputTag can be used in conjunction with an EventSetup Record to retrieve a particular data
0014  item from the Record.  The EventSetup uses two pieces of information to find data in a Record
0015     1) the C++ class type of the data
0016     2) an optional string which we will refer to as the 'dataLabel'
0017  The dataLabel is used to differentiate objects of the same type placed in the same Record.
0018
0019  In addition, every piece of data in the EventSetup comes from either an ESSource or an ESProducer.  Every
0020  ESSource and ESProducer is assigned a label (referred to here as the moduleLabel) in the configuration of
0021  the job.  This label may be explicitly set or it may just be the C++ class type of the ESSource/ESProducer.
0022  For example, say there is an ESProducer of C++ class type FooESProd. If the python configuration has
0023        process.FooESProd = cms.ESProducer("FooESProd", ...)
0024  then the module label is 'FooESProd'.
0025  If the python configuration has
0026        process.add_( cms.ESProducer("FooESProd", ...)
0027  then the module label is also 'FooESProd'.
0028  However, if the python configuration has
0029        process.foos = cms.ESProducer("FooESProd",...)
0030  then the module label is 'foos'.
0031
0032  The ESInputTag allows one to specify both the dataLabel and moduleLabel.  The dataLabel is used to find the data
0033  being requested.  The moduleLabel is only used to determine if the data that was found comes from the specified
0034  module.  If the data does not come from the module then an error has occurred.  If the moduleLabel is set to the
0035  empty string then the data is allowed to come from any module.
0036
0037  Example 1:
0038  FooESProd makes Foos with the default dataLabel ("")
0039  The module is declared in the python configuration as
0040      process.FooESProd = cms.ESProducer("FooESProd",...)
0041  The following python configurations for ESInputTag can be used to get its data
0042      cms.ESInputTag("")
0043      cms.ESInputTag(":")
0044      cms.ESInputTag("","")
0045      cms.ESInputTag("FooESProd")
0046      cms.ESInputTag("FooESProd:")
0047      cms.ESInputTag("FooESProd","")
0048
0049  Example 2:
0050  FooESProd makes Foos with the dataLabel "bar"
0051  The module is declared in the python configuration as
0052      process.FooESProd = cms.ESProducer("FooESProd",...)
0053  The following python configurations for ESInputTag can be used to get its data
0054      cms.ESInputTag(":bar")
0055      cms.ESInputTag("","bar")
0056      cms.ESInputTag("FooESProd:bar")
0057      cms.ESInputTag("FooESProd","bar")
0058
0059  Example 3:
0060  FooESProd makes Foos with the default dataLabel ("")
0061      process.FooESProd = cms.ESProducer("FooESProd",...)
0062  Foo2ESProd also makes Foos with the default dataLabel ("")
0063      process.Foo2ESProd = cms.ESProducer("Foo2ESProd",...)
0064  The jobs has an ESPrefer which states Foos should come from FooESProd
0065      process.perferedFoo = cms.ESPrefer("FooESProd")
0066  Then to get the data, one can specify the ESInputTag identical to Example 1.
0067  However, the following ESInputTags will lead to an exception begin thrown
0068      cms.ESInputTag("Foo2ESProd")
0069      cms.ESInputTag("Foo2ESProd:")
0070      cms.ESInputTag("Foo2ESProd","")
0071  The exception happens because FooESProd is the only allowed source of Foos
0072  but the ESInputTag says you really wanted them to come from Foo2ESProd.
0073 */
0074 //
0075 // Original Author:  Chris Jones
0076 //         Created:  Thu Feb 19 13:01:38 CST 2009
0077 //
0078
0079 // system include files
0080 #include <iosfwd>
0081 #include <string>
0082
0083 // user include files
0084
0085 // forward declarations
0086 namespace edm {
0087   class ESInputTag {
0088   public:
0089     explicit ESInputTag();
0090     explicit ESInputTag(std::string iModuleLabel, std::string iDataLabel);
0091     explicit ESInputTag(const std::string& iEncodedValue);
0092
0093     // ---------- const member functions ---------------------
0094
0095     /**Returns the label assigned to the module for the data to be retrieved.
0096        If the value matches the defaultModule value (which is the empty string)
0097        Then no match is attempted with the module label.
0098        */
0099     const std::string& module() const { return module_; }
0100
0101     /**Returns the label used to access the data from the EventSetup.
0102        The empty string is an allowed (and default) value.
0103        */
0104     const std::string& data() const { return data_; }
0105
0106     bool operator==(const edm::ESInputTag& iRHS) const;
0107
0108     std::string encode() const;
0109
0110   private:
0111     // ---------- member data --------------------------------
0112     std::string module_;
0113     std::string data_;
0114   };
0115
0116   std::ostream& operator<<(std::ostream&, ESInputTag const&);
0117 }  // namespace edm
0118
0119 #endif